Power Smoothing Control Strategy of Doubly-fed Induction Generator Based on Constraint Factor Extent-limit Control

On the basic analysis of the operating characteristics of doubly-fed induction generator(DFIG) and conventional control strategy of maximum power point tracking(MPPT),a new control strategy based on constraint factor for extent-limit to smooth the active power output of DFIG was proposed.This method could provide a adjustable limit value of active power output,which combined the generator speed control and pitch angle control to keep the active power output at any given value.The expression and calculation method of constraint factor was provided.Based on Matlab/Simulink emulation,the active power output characteristic of a 9MW wind farm was researched by the proposed smooth control strategy.Smooth performance index and variance were respectively computed with conventional and proposed method.Experiment results demonstrate that active power fluctuation is obviously weakened by the proposed control strategy and electric power system quality is promoted compared with the conventional MPPT control method.